Carpet tile assemblies are widely used as floor coverings, as they provide a number of advantages over their broadloom counterparts. Because such tiles are provided in relatively small dimensions, e.g. generally in the form of 18 inch by 18 inch, or 36 inch by 36 inch squares, they can be used to achieve a variety of visual design effects. In addition, the lifespan of the overall floor covering can be increased, as individual tiles that become stained or damaged can be repaired of replaced without the need for replacement of the entire floor covering.
In addition, the installation of carpet tiles can in some cases be preferable to the installation of broadloom (i.e. wall-to-wall type) carpet, since the tiles can be selected and cut to conform to corners and irregularities in the floor dimension. In contrast, it can often be difficult to cut a large piece of broadloom to exact conformance with the room, since it can be difficult to integrate a number of irregularities or corners at once. Furthermore, because it is generally considered to be desirable to minimize the number of seams in a broadloom carpet installation, it is often the case that the largest piece of broadloom carpet available for use in a particular room installation is selected. This can present challenges with respect to storage and transport in addition to the obvious difficulties associated with working with a large piece of material during installation.
However, heretofore in actual practice it has not been possible to fully maximize the advantages associated with carpet tiles. Specifically, conventional methods for the installation of carpet tiles require the use of relatively strong adhesives to bond the tiles to the existing floor structure. In one common installation method, the installer coats the floor with an adhesive, allows the adhesive to set up, then secures the tiles to the floor by pressing them onto the adhesive. Typically, this involves spreading a layer of adhesive over the entire floor surface.
As will be readily apparent to those of ordinary skill in the art, this method requires that the installer sit or stand on the installed tiles., since he cannot step on the adhesive-covered floor. This can result in inadvertent slipping of the tiles as the adhesive is curing due to shifts in the installer's body weight as he reaches to install the next tile. This can in turn lead to irregularities in the appearance of the installation. In addition, the process can be awkward since the installer is forced to pull the tiles into position, and can result in a failure to achieve a tight junction between adjacent tiles. Furthermore, this method makes it possible for the carpet tiles to become damaged or soiled by the installer as they are installed. Therefore, the skill of the installer can be a critical factor in the overall quality and look of the carpet tile installation.
A further difficulty associated with the use of adhesively attached tiles is that the wet adhesives typically include volatile organic compounds (VOCs). To reduce any potential health risks to the installer from breathing too many fumes, it is generally considered to be important to insure that the installation environment has adequate ventilation to remove the adhesive fumes.
A further disadvantage of adhesive installed carpet tiles is the cost associated with the adhesive material and the time and manpower associated with the application of the adhesive. There is also a cost associated with the inefficient recycle, refurbishment or reuse of the tiles since many carpet tiles are damaged during removal and must be discarded by land filling, incineration or other methods none of which are environmentally desirable.
To overcome the problems associated with the installation of carpet tiles using wet adhesives, it has been proposed to provide the tiles with a pre-coat of adhesive, which is protected by a release sheet. While eliminating some of the problems associated with VOCs and the like, this method presents several of its own disadvantages not the least of which is added material costs and production costs.
Also, the release sheets, which are generally in the form of a coated paper sheet, must be disposed of following their removal from the squares. In addition, if a portion of the release sheet on a tile comes loose, the underlying surface of the tile bottom surface can lose its adhesive capabilities, meaning that the tile will not be fully secured to the floor structure about the entire dimension of the tile. This can particularly become an issue when the tiles must be cut to accommodate corners of a room or other irregularities in the room dimension. Similarly, if a portion of a release sheet comes loose from a tile prematurely, the adhesive can stick to an adjacent tile, which can result in damage to one or both of the tiles when the tiles are subsequently separated.
The use of a pre-coat adhesive does not mitigate the cost associated with materials or the problems associated with carpet tiles which are damaged upon removal of adhesive attached tiles.
A further disadvantage associated with the two above-described adhesive and pre-cost installation methods is that they require that the flooring to which the carpet tiles are to be secured be extremely clean and dry. Any dirt, dust or other foreign matter present (as well as flooring irregularities) can interfere with proper adhesive attachment of the carpet tile.
In addition, the removal of the adhesively-attached tiles presents problems in itself. In some cases, removal of the tiles can result in damage to or destruction of the tiles (or floor); this is particularly disadvantageous in view of the emerging methods for recycling and refurbishing used carpet tiles, which require that the tiles be substantially undamaged for them to be available for further processing. In addition, adhesive material that remains on the rear surface of carpet tiles can adversely affect the appearance of the refurbished tiles.
Such residual adhesive also presents problems for the flooring to which the tiles were attached, as it can be difficult as well as labor intensive to remove all of the adhesive. In fact, some property owners are hesitant to install carpet tiles, out of concern over the effects of the adhesive on the existing flooring when the tiles are removed. This is a particular problem if carpet tiles are to be used most efficiently. One great advantage to carpet tiles is the ability to replace individual tiles instead of the entire carpet. If a single tile, or a small section of tiles, is removed it is extremely difficult to clean the adhesive remaining on the floor without deleterious effects on the remaining tiles. This has thwarted efforts to expand the usage of carpet tiles since a major advantage is diminished by the remaining adhesive.
Carpet tiles are generally provided in the form of squares of carpeting material secured to a relatively thin, rigid backing, which is designed to assist the tile in remaining flat on the floor. Because the individual tiles have relatively small perimeter dimensions, a body traveling across a carpet-tiled expanse comes into contact with a number of tile edges at the junctures of adjacent tiles. Similarly, a body rolled across a carpet-tiled expanse results in the individual tiles contacted being subjected to lateral forces, which can cause a tile to press laterally against an adjacent tile. It therefore frequently results that the lateral forces cause tiles to pop out over the edge(s) of the adjacent tiles. It is for this reason that the provision of a strong adhesive layer bonding the carpet tiles to the floor has conventionally been seen to be so critical.
Attempts have been made to provide substitutes for the adhesive bonding of the carpet tiles to the floor. For example, U.S. Pat. No. 4,731,275 to Andersen describes a carpet tile assembly designed to resist lateral movement. The assembly includes a layer of elastomeric material vulcanized to the carpet layer, with a plurality of protrusions and spikes being provided thereon for mating with a base layer of material, such as a felt-like fiber mat. This assembly therefore requires that the base layer be secured to the floor, which would add dramatically to the cost of installation. Furthermore, while the Andersen patent purports to address the problems associated with the removal of adhesives from the floor, the method contemplates the use of adhesives as an option for securing the base layer to the floor.
U.S. Pat. No. 4,571,353 to Gable, Jr. describes interlocking carpet tiles. Each tile has shaped side edges so that the tiles can interlock with adjacent tiles to minimize movement of the tiles in relation to each other. The Gable patent discusses the fact that free-lay tiles have a tendency to buckle, curl and warp after use. The Gable tiles are described as also having a bottom layer of thermoplastic material, with the material having indentations or other designs on its bottom surface, in order to increase the coefficient of friction with the floor. As will be readily appreciated by those of ordinary skill in the art, this construction requires additional manufacturing expense and the construction would be much more difficult to install than conventional carpet tiles due to the interlocking nature of the individual tiles.
Similarly, U.S. Pat. Nos. 4,010,301 and 4,010,302 to Anderson et al. describe carpet tiles designed to have, among other things, improved floor hugging properties. To this end, the carpet tiles described in the '301 and '302 patents include a backing layer of thermoplastic material (e.g. natural or synthetic rubber, or thermoplastic material) having a series of friction-increasing indentations or corrugations. The backing layer is illustrated as being relatively thick, and is described as being applied in the form of a relatively stiff plastisol, leveled by a doctor blade, heated and embossed by an embossing roll to form indentations on the bottom surface.
As discussed in Textiles for Residential and Commercial Interiors, by Jan Yeager, (1986), pp. 334–335, the disclosure of which is incorporated herein by reference, attempts have been made to produce “free lay” carpet tiles of the rigid carpet tile variety. However, it was recognized that such installations could only be used where heavy rolling traffic would not be expected, as such would have a “snowplow” effect, raising the edges of the tiles. In an attempt to achieve a rigid free lay carpet tile, it was suggested to apply a heavy secondary backing (e.g. through the application of a heavy secondary backing such as alternate layers of heavy-gauge vinyl and glass fiber scrims) to provide increased dimensional stability. Even with this reinforcement, it was suggested that it would be desirable in many cases to glue down at least 10–20% of the carpet tiles in order to achieve satisfactory performance. Therefore, although prior products have categorized themselves as “free lay”, such terminology is understood in the art to describe products having a reduced amount of adhesive securing them to the floor, such adhesive typically being applied in a grid pattern.
Since the introduction of carpet tiles, advances have been made in their construction, including the development of carpet tiles having cushion. Such tiles have been found to provide superior comfort to individuals walking on, standing on, or otherwise using the installations. Because the cushion tiles do not typically have the heavy rigid reinforcement of their rigid carpet tile counterparts, it would therefore be expected that the cushion backed tiles would require even more adhesive to obtain satisfactory securement to the floor, particularly where rolling traffic would be expected. For example, carpet tile manufacturers recommend that manufacturers use at least a grid of adhesive material to secure hard-back tiles, while recommending the use of a full adhesive layer beneath cushion-backed tiles.
Commonly-assigned U.S. Pat. No. 4,522,857 describes a prior attempt to produce free-lay cushion backed carpet tiles. While representing an advance over the prior art, the carpet tiles described in that patent still required the use of a grid of adhesive to keep them in proper position during use, particularly when encountering rolling traffic.